The development of a high dielectric material to be used in an embedded type passive device such as an inductor, a resistive material, or the like, as well as a large-area capacitor has been required. In general, as a method for forming a high dielectric insulation film, there is a method for forming a composite of ceramic or metal particles and a polymer material to use the formed composite as a high dielectric material. However, due to a difference in chemical and physical properties between the polymer and the ceramic or metal particles, it is difficult to effectively disperse the ceramic or metal particles, such that it is difficult to improve physical properties through composite formation.
Therefore, composite formation of inorganic or metal nanoparticles with a polymer matrix may be performed by organic surface treatment, which is performed for various purposes in various forms. In the case of treating the inorganic or metal nanoparticles with an apolar organic layer, dispersibility of particles in an apolar medium is increased, such that the inorganic or metal nanoparticles may be treated with a homogeneous dispersion solution. Particularly, in the case in which the dispersion medium is a polymer, a polymer-inorganic particle or polymer-metal particle nanocomposite is formed due to this function, such that physical properties of the polymer are improved, thereby making it possible to be applied to various materials for a high dielectric thin film, a high strength construction material, a high barrier film, various function films, or the like.
As an organic surface treatment method of the inorganic or metal nanoparticles as described above, an attaching method to a surface by chemical bonds using functional groups of monomolecular materials, an attaching method by physical adsorption caused by an electrostatic interaction, or the like, using functional groups of monomolecular materials, a coating method by coagulation of polymer materials formed on surfaces of particles, a coating method by chemical bonds between functional groups of a polymer chain and surfaces of particles or physical adsorption caused by an electrostatic interaction therebetween, and the like, have been widely used, but in the case of separately performing surface treatment on the inorganic or metal nanoparticles, there are problems in that a process becomes significantly complicated, and a cost and time are increased.
Further, since a polymer composite film having excellent performance may be formed through hybrid particles coated with polyimide and composite formation of the hybrid particles in a polymer matrix due to inherent excellent heat resistance, chemical resistance, and mechanical properties of polyimide, a method using polyimide has been spotlighted among methods for treating surfaces of inorganic or metal nanoparticles with a polymer material. However, in the case of forming a polyimide layer enclosing inorganic particles by simple coagulation of polymer chains, there is a problem in that a stable and uniform interface of polymer-inorganic or metal particles may not be sufficiently formed. Polyimide is formed by preparing polyamic acid as a precursor and imidizing polyamic acid due to characteristics of a manufacturing process. Since in a polyamic acid state, a carboxyl group is present in each repeating unit of a polymer chain, it is considered that an electrostatic interaction with inorganic or metal nanoparticles is large and a stable polymer coating layer is formed, but when the imidization of polyamic acid into polyimide is completed, the carboxyl group is not present in the polymer chain, such that the interaction with the inorganic particles becomes weakened, and it is difficult to completely coating the surfaces of the inorganic particles.
A high dielectric thin film prepared by a composite of inorganic nanoparticles coated with a block copolymer and a polymer matrix has been disclosed in Korean Patent No. 10-0963648 (Patent Document 1), and a polyimide-inorganic particle composite obtained by preparing polyamic acid including a poloar functional group, preparing polyimide-inorganic particles using the polyamic acid, and coating the polyimide-inorganic particles on a polymer matrix has been disclosed in Korean Patent Laid-Open Publication No. 10-2010-0124624 (Patent Document 2).
At the time of preparing the inorganic or metal nanoparticle-polymer composite according to the related art as described above, surface treatment such as organic surface treatment, or the like, of the nanoparticles, or an additional process such as introduction of a functional group in a polymer for coating the particles, or the like, has been required, such that a process cost and process time are increased.